DC not appearing in domain

I've googled this, yet the solutions I've found haven't fully resolved my issue. I'm hoping someone here may have some advice. I can supplement the information here, should there not be enough, just let me know.

I recently set up a 2008 Enterprise Server R2. This server was implemented to be the new domain controller for an existing domain. The previous DC was a 2003 Standard. The move went smoothly, all files, permissions, roles, etc. The old DC was demoted, and remains as a member server should any missing file issues arise.

There are also two additional new servers (2008 Storage, and 2008 Enterprise to function as an Exchange box in the future.) These are simply member servers as well.

This week, in response to the customer's continuous requests to open RPD ports for folks to reach their office workstations from home, my supervisor decided to enact a VPN role on the server, using information he found on the internet. The result took the server offline and unresponsive to his attempts to re-establish an RPD session with it. He called the customer and walked her through removing the role, which initially appeared to be successful.

Yesterday, I had to drive out to the account and reapply the role, disable the Routing and Remote Access, and remove the role again to get the server to respond to DNS requests, and shared drives, etc.

Today the customer calls to report she cannot see the DC on the domain when she browses the network. In addition, my supervisor finds that he cannot see the domain workstations under the DC's Network screen, which we could before with no problem. He believed the problem to be that he couldn't enable "Turn on Network Discovery" and sent me out to fix it.

I googled this, and found the services necessary to enable Network Discovery (i.e. nscache, fdrespub, ssdpsrv, and upnphost.) Afterwards, the only ones in the domain that can see the DC by browsing are the two 2008 servers. None of the workstations (all XP) and the 2003 server cannot find the DC via browse, but can ping it by name and IP, and can access the shares using the standard \\server\ in the Run box. Add to this, the DC cannot see anything in the domain via browse except the 2008 Storage server.

I've spent several hours today going through services and policies and reading a number of online articles and white papers, and I cannot resolve the issue. I'm hoping someone here may be able to point me in the right direction.

Thanks in advance.